We could never find the yellow drainage tune so we used 3.0" gas line, it is WAY ($2.41 per ft. and that was my vendor price from my supplier) more expensive than the drainage tubing. I googled my Arse off for the drain tube, hopfully someone can post a distributer.
I know they use it on baseball fields also in our area, I am sure it is around, I just couldn't locate any last year. Let us know